Similarly, The templates I custom build all have separate subsets for different phases. They're not really different layout books as such, but the result is the same.
Don't forget to make separate publishing sets for each phase (by using shortcuts).
This is really an effective and efficient way to document small - medium projects. Although GS recommends splitting up larger projects, it would have to be pretty large to convince me to do it.
So far the biggest problems in doing this are if you want to use the numbering system such as Page X of Y, as there is no capability to list just the numbers of pages in a subset, so all pages in the layout book are included. Long workarounds are available as discussed
here.
Also it is cumbersome to create one single sheet index with each phase listed separately, as the criteria for an index allows us to select just one Subset at a time. This has been been discussed many times, including
here with a bit of a workaround.
Cheers,
Link.